Paper treatment

ABSTRACT

A method of improving the electroconductivity of paper comprising applying to at least one surface of the paper an aqueous solution of a polymer or copolymer of a quaternary ammonium chloride or acetate derived from an aminoalkyl acrylate or methacrylate, the polymer or copolymer having an average molecular weight in the range 5,000 to 2,000,000. The treated paper is suitable as base paper for electrographic printing.

Cowling et a1.

1 1 PAPER TREATMENT [75] Inventors: Ronald Cowling; James NairnGreenshields, both of Manchester, England [73] Assignee: ImperialChemical Industries Limited, London, England [22] Filed: Nov. 23, 1973[21] Appl. No.: 418,184

Related US. Application Data [63] Continuation of Ser. No. 115,844, Feb.16, 1971,

abandoned.

[30] Foreign Application Priority Data Feb. 25. 1970 Great Britain9115/70 [52] US. Cl 117/201, 96/15, 117/155 R, 117/155 UA. 117/161 UN[51] Int. Cl B44d 1/18, 603g 7/00 [58] Field of Search.. 117/155 R, 155UA, 161 UN, 117/201, BIG. 4; 162/138; 96/15 [56] References Cited UNITEDSTATES PATENTS 3,486,932 12/1969 Schaper et a1. 117/201 Mar. 11, 19753,544,318 12/1970 Boothe et a1. 117/201 3,615,408 10/1971 Taubman 96/1.53,617,372 ll/1971 McNamee et a1. 117/201 3,619,284 11/1971 Ray-Chaudhuriet a1 117/201 3,640,766 2/1972 Jursich et al 117/201 PrimaryExaminerDanie1 .l. Fritsch Attorney, Agent, or Firm-Cushman. Darby &Cushman [57] ABSTRACT 3 Claims, No Drawings PAPER TREATMENT This is acontinuation, of application Ser. No. 115,844 filed Feb. 16, 1971 nowabandoned.

This invention relates to a method of paper treatment and moreparticularly to a method of improving the electroconductivity of paper.

It has already been proposed to provide paper suitable for use invarious copying processes by treating the paper with materials toimprove the electroconductivity.

The present invention provides a method of improving theelectroconductivity of paper which comprises applying to at least onesurface of the paper an aqueous solution of a polymer or copolymercontaining in the molecule repeating units of the formula:

-CH -CR- 1 wherein R represents hydrogen or methyl, R represents methylor ethyl, R and R each independently represents methyl or ethyl or R andR taken together represent Cl-l CH OCH CH or (CH )n where n represents4, 5 or 6, A represents alkylene or substituted alkylene and Xrepresents a chloride or ac etate ion, said polymer or copolymer havingan average molecular weight in the range 5,000 to 2,000,000.

Preferably the polymer or copolymer has a molecular weight of from10,000 to 500,000.

Alkylene radicals which may be represented by A in Formula 1 includeethylene. Substituted alkylene radicals include hydroxy-substitutedalkylene radicals, for example 2-hydroxytrimethylene.

The polymers or copolymers to be used in the method of the presentinvention may be prepared by the free radical catalysed polymerisationof a monomer CH =CRCOOAN R R R X, optionally with a further vinylmonomer, or by the free radical catalysed polymerisation of CH=CRCOOANRR optionally in the presence of a further vinyl monomerfollowed by quaternisation of the polymer or copolymer with a suitablequaternising agent.

Suitable copolymers for use according to the present inventionpreferably contain at least on a weight basis of units of Formula I.Co-monomers of the vinyl series which may be used in preparing thecopolymers include styrene, methyl methacrylate, methyl acrylate, ethylacrylate, butyl acrylate, ethylhexyl acrylate, acrylonitrile, vinyltoluene, vinyl acetate, B-ethoxyethyl methacrylate, B-hydroxyethylmethacrylate, ethylene glycol dimethacrylate, acrylamide, diacetoneacrylamide, ethylene, propylene and divinyl benzene.

In the case of copolymers utilising as the comonomer one which forms awater-insoluble polymer, the proportion of the said co-monomers must besuch that the copolymers are soluble in water.

Unexpectedly, it has been found that copolymers having a comparativelyhigh proportion of nonquaternary units can increase the conductivity ofpaper substantially as effectively as a quaternary homopolymer.Particularly useful non-quaternary units in this respect are thoseformed by the use of styrene, vinyl toluene, Z-ethylhexyl acrylate andmethyl methacrylate. Copolymers contain 15-80% by weight of units of Formula l are both effective and economically attractive.

in addition to the economic advantages which can be gained by using acheap non-quaternary comonomer, a further and unexpected advantage canaccrue, that is an improvement in solvent holdout. Solvent holdout is ameasure of the treated papers ability to prevent penetration of organicsolvents into the paper. A good solvent holdout is required in acommercial Electrofax base paper to prevent penetration of thesolvent-borne photoconductive agent into the electroconductive basepaper.

The solution of polymer or copolymer may be applied to the paper by anyconvenient method, for example by coating, dipping, brushing or wet endaddition. The polymer or copolymer may be applied from an aqueoussolution or an aqueous composition containing the polymer or copolymertogether with one or more additives which may improve the applicationproperties or the properties of the finished paper. Suit: able additivesinclude starch, water-soluble cellulose derivatives, polyvinyl alcohol,calcium carbonate and pigments. The amount of polymer or copolymer to beapplied to give the desired electroconductive properties may be easilydetermined by trial.

Paper treated according to the method of the present invention isparticularly suitable as a base paper for electrographic printing.

The invention is illustrated but not limited by the following Examplesin which all parts and percentages are by weight.

EXAMPLE 1 A sized bleached chemical wood pulp paper of g. per sq. metreis coated on one surface with a 3.7% aqueous solution of apoly(trimethyl-B- methacryloyloxyethyl ammonium chloride), having anumber average molecular weight of 52,000 to give a coating weight oflg./sq. metre (expressed as dry polymer solids). After standing for 48hours in a cabinet having a circulating atmosphere at 20C. and 20%relative humidity, the surface resistance is measured between two 1 inchsquare brass electrodes, at a potential difference of 500 volts DC,placed 1 inch apart on the treated surface of the paper. The resistanceis found to be 3.9 X 10 ohm.

For comparison the untreated paper and a paper coated in the same manneras above, but using Calgon 261, a commercially available product,(Calgon is a Trade Mark of Calgon Corp.) are tested, giving 3 X l0'ohmand 6 X 10 ohm respectively.

EXAMPLE 2 The surface resistivities of paper coated and tested as inExample 1 are given in the following table.

Polyquaternary number coating surface average weight g/ resistivity 1molecular sq. metre (ohms) weight Copolymer of equimolar amountstrimethyl B-methacryll 9.0 X l0 oyloxyethyl ammonium chloride 2 1.7 XIt)" and styrene Poly(diethyl methyl 3- methacryloyloxyethyl ca. 150.0001 17 X l0 ammonium acetate) Poly(methyl-Bmethacryloyloxyethylpyrrolidinium 162.000 l 2.3 X l0 chloride) 2 0.44 X It)"poly(methyl-B-methacryloyloxyethyl piperidinium 138,000 I 28 X l0chloride) poly(diethyl methyl-Bmethacryl- 400.000 l 9.3 X l0"oyloxyethyl ammonium chloride poly(methyl-62 -methacryloyloxy- 42,000 l53 X ethyl morpholinium chloride) EXAMPLE 3 The surface resistivities atrelative humidity of paper coated at 1 gm with various copolymers and ahomopolymer for comparison are presented in the following table.

reverse side. The solvents used are toluene and lsopar G (Esso PetroleumCompany).

[Go] Polymer Quaternary Unit Non-quat. Molar Number Surface Unit Ratioaverage Resistivity Quat: molecular (ohms) Non-quart weight 8 -CH -C (C50:50 52,000 5-9 x 10 2 H3 Z &O:6O 4-7 x 102 COOCH CH NHQ :70 7-1 x 10 325:75 20 x 10 ci 8 61-1 :50 47.000 10.5 x 10 I tO=6O 7.0 x 10 -Cfl -C-30:70 10.5 x 10 COOtIl-I -CH -C(CH homopolymer l i 5 5 x 10 COOCH C-I'IIMe Cl i 8 Untreated Paper 3000 x 10 EXAMPLE 4 Solvent hold-out isdetermined by pipetting 2 ml. of I All agents are coated at 1 gm on tothe same quality of gm. paper.

[Go] Polymer Pin Holes per Sq.Inch

Quaternary unit Non-quat Molar Toluene Isopar G Unit ratio COOCH CHNI-ie 3 -caca 50:50 c1 2 ao=6o 4 4 30:70 20 18 -C1'I O(H )0OQCH CH MQCJ. Hemopolymcr 3 Polyhinylbengyl trimethyl ammonium chloride) 14 15 Thepoly(vinylbenzyl trimethyl ammonium chloride) used is a commerciallyavailable product marketed as an electroconductive resin for paper andis included for comparison.

EXAMPLE 5 A range of copolymers, containing 57% of units of the formula-CH C(CH) and 43% of units derived from a non-quaternary conomoner, werecoated on to paper at 1 gm and the surface resisitivity measured at RHand C. using 500 V DC. applied across the annular gap between 5 and 7cm. concentric electrodes (British Standard 903). The results obtainedare presented in the following table.

A starch solution is prepared by making a paste from 60 parts of acationic starch and 60 parts of water. 280 Parts of boiling water areadded and the mixture is stirred for 15 minutes at 90C. To 90 parts ofthe cooled starch solution is added 22.4 parts of a 36.1% aqueoussolution of a trimethyl 2-methacryloyloxyethyl ammonium chloride/styrene40:60 molar copolymer. A

further 22.6 parts of water are added and the mixture stirred to give apale coloured solution having a slight haze due to the starch.

The coating mix is applied to paper to give a coat weight of 1.5 gm" ofelectroconductive resin per side. The surface resistivity is measured at20% RH and 25C. using the electrodes described in Example 5.

The treated paper has a surface resistivity of 4.] X 10 ohm, whereasthat of the untreated paper is 27 X 10 ohm.

We claim:

1. A method of improving the electroconductivity of paper whichcomprises applying to at least one surface of the paper an aqueoussolution of a copolymer containing in the molecule 15-80% by weight ofrepeating units of the formula:

0001-1 CH N --R wherein R represents methyl or ethyl, R and R eachindependently represents methyl or ethyl or R and R taken togetherrepresent CH CH OCH CH or (CH2)n where n represents 4 or 5 and Xrepresents a chloride or acetate ion, the remainder of the copolymerconsisting of styrene, vinyl toluene, 2-ethylhexyl acrylate or methylmethacrylate units, said copolymer having an average molecular weight inthe range 5,000 to 2,000,000.

2. A method as claimed in claim 1 wherein the copolymer has an averagemolecular weight of from 10,000 to 500,000.

3. A method as claimed in claim 1 wherein R, R and R are each methyl andX is chloride.

1. A METHOD OF IMPROVING THE ELECTROCONDUCTIVITY OF PAPER WHICHCOMPRISES APPLYING TO AT LEAST ONE SURFACE OF THE PAPER AN AQUEOUSSOLUTION OF A COPOLYMER CONTAINING IN THE MOLECULE 15-80% BY WEIGHT OFREPEATING UNITS OF THE FORMULA:
 1. A method of improving theelectroconductivity of paper which comprises applying to at least onesurface of the paper an aqueous solution of a copolymer containing inthe molecule 15-80% by weight of repeating units of the formula:
 2. Amethod as cLaimed in claim 1 wherein the copolymer has an averagemolecular weight of from 10,000 to 500,000.